In a typical restaurant kitchen, a plurality of cooking units are lined up side by side in a row under a common exhaust hood. The cooking units may include, for example, ranges, griddles, fryers, and broilers. They all produce air laden with grease, smoke, fumes, moisture, and heat in varying amounts and temperatures. Low temperature cooking equipment such as ranges and griddles produce considerably less amounts of such pollutants in comparison to high temperature equipment such as broilers. Traditional ventilation apparatus are unable to adjust or regulate the airflow in segments within the filter area of the hood. Therefore, to exhaust all of the pollutants and heated air produced from the cooking equipment, traditional ventilation apparatus provide excess ventilation for cooking units such as ranges and griddles in order to capture the large quantities of pollutants produced by broilers and fryers. To increase efficiency, some have modified traditional kitchen ventilators with inlet throat choke attachments in air inlet regions associated with low-pollutant cooking units. The inlet throat choke attachments reduce or throttle the flow of air through portions of the ventilator where the maximum available rate of air removal is not required to remove the pollutants generated by the associated units. U.S. Pat. No. 4,281,635 issued Aug. 4, 1981 to Gaylord discloses one such kitchen ventilator.
The installation of the supplemental inlet throat choke attachments into an existing ventilation hood requires taking apart the ventilation apparatus. The installation, removal, and adjustment of the choke attachments are difficult and time-consuming. Further, pollutants such as grease and particulates carried by the air accumulate on the choke attachments and surrounding areas, which need to be cleaned periodically. Typical water-washed ventilation hoods employ water streams that cannot reach the different sides of the choke attachments disposed at various angles. The accumulation of the pollutants have a negative impact on the ventilation system, and create unsanitary conditions and fuel for any fire within the ventilation apparatus. In addition, because there are different types and sizes of ventilation hoods and different attachments of the cooking units, the choke attachments will typically need to be custom-designed to achieve the maximum benefits.
Some have designed exhaust hoods that are adjustable to achieve improved ventilation. For instance, U.S. Pat. No. 5,522,377 to Fritz discloses an adjustable exhaust hood that includes an open underside and a grease filter defining an exhaust plenum between the hood and the grease filter and a flow path through the grease filter. A shutter-like panel is slidable into the flow path adjacent to the grease filter for blocking a portion of the flow path to adjust a volume of air flowing through the exhaust hood. Fritz also discloses the use of multiple side-by-side panels.